Differential motion sensor

ABSTRACT

A differential motion sensor includes a base and a cradle. The base includes a first surface that extends along a first axis to define a length and a second axis to define a width. The base further includes at least one hinge that pivots about a rotational axis extending along the first axis. The cradle is pivotably coupled to the at least one hinge and is configured to move in the direction of the second axis when pivoting about the hinge. The differential motion sensor is configured to operate in a first mode when the cradle is aligned with the base and a second mode when the cradle is pivotably displaced with respect to the base.

BACKGROUND OF THE INVENTION

The present disclosure generally relates to differential motion sensingand, more particularly, to slat differential motion sensors.

Differential motion sensors can be used to detect displacement ofadjacent objects and/or components. Slat differential motion sensors,for example, can be used to detect displacements and skews of aircraftcontrol surfaces, such as slats or flaps on aircraft wings. Thedisplacement of the slats may be caused, for example, by an actuatordisconnection from the surface it drives.

Conventional slat differential motion sensors typically employ twohinged arms configured to move independent from one another. The armsare connected by an electromechanical fuse. The slat differential motionsensor is typically mounted to a first panel, while a striker pin isconnected to a second panel. A system controller is provided to monitorcontinuity at the fuse and the status of the sensor. When abnormaldifferential motion occurs, the fuse is loaded in tension (i.e.,realizes a tensile force) and fractures the fuse, annunciating thefailure to the system controller. Conventional slat differential motionsensors, however, are affected by the spanwise motion (i.e., motionparallel to the span of an aircraft wing) of the panels. Spanwise motionresults in significant variation of forces acting upon the fuse whichhas to be designed to assure functional repeatability of skew detectionwithout nuisance signaling to the system controller. Greater spanwisemotion, for example, results in a lower pin force but a less sensitivesensor.

BRIEF DESCRIPTION OF THE INVENTION

According to a non-limiting embodiment, a differential motion sensorincludes a base and a cradle. The base includes a first surface thatextends along a first axis to define a length and a second axis todefine a width. The base further includes at least one hinge that pivotsabout a rotational axis extending along the first axis. The cradle ispivotably coupled to the at least one hinge and is configured to move inthe second direction when pivoting about the hinge. The differentialmotion sensor is configured to operate in a first mode when the cradleis aligned with the base and a second mode when the cradle is pivotablydisplaced with respect to the base.

According to another non-limiting embodiment, a method of detectingdisplacement of a first object with respect to a second object includesforming a base on the first object. The base includes a first surfaceextending along a first axis to define a length and a second axis todefine a width. The method further includes pivotably connecting acradle to the base such that the cradle is configured to move in thesecond direction. The method further includes detecting that the firstand second objects are aligned with respect to one another when thecradle is aligned with the base, and detecting that the first and secondobjects are displaced with respect to one another when the cradle ispivotably displaced with respect to the base.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a differential motion sensor accordingto a non-limiting embodiment;

FIG. 2A is a side view of a differential motion sensor operating in aclosed-circuit mode according to a non-limiting embodiment; and

FIG. 2B illustrates the differential motion sensor of FIG. 2A operatingin an open-circuit mode according to a non-limiting embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, a differential motion sensor 100 is illustratedaccording to a non-limiting embodiment. The differential motion sensor100 includes a base 102 and a cradle 104 pivotably connected to the base102. The base 102 includes a first surface 106, a first base arm 108 a,and a second base arm 108 b. The base 102 extends along a first axis(e.g., an X-axis) to define length, a second axis (e.g., a Y-axis)perpendicular to the first axis to define a width, and a third axis(e.g., a Z-axis) perpendicular to the first and second axes to define aheight. According to a non-limiting embodiment, the base 102 can becoupled against a surface of a first panel (not shown in FIG. 1) asdiscussed in greater detail below. The first base arm 108 a extends froma first side of the base 102 in the Z-axis direction, and the secondbase arm 108 b extends from a second side of the base 102 opposite thefirst side in the Z-axis direction. The first side of the base 102includes a first hinge 110 a and the second side of the base 102includes a second hinge 110 b. Each of the first and second hinges 110a/110 b pivots about a rotational axis (A) extending along the Y-axis.The first and second hinges 110 a/110 b are both pivotably coupled tothe cradle 104 as discussed in greater detail below.

The cradle 104 includes a first cradle arm 112 a and a second cradle arm112 b disposed opposite the first cradle arm 112 a. Each of the firstand second cradle arms 112 a/112 b includes a first end and a secondend. A surface of the cradle 104 includes a pair of opposing crossbars114 a/114 b extending along the Y-axis and between the first end of thefirst and second cradle arms 112 a/112 b to define a cradle opening 116.The second end of the first cradle arm 112 a is pivotably connected tothe first hinge 110 a, and the second end of the second cradle arm 112 bis pivotably connected to the second hinge 110 b. In this manner, thecradle 104 (and thus the cradle opening 116) is configured to move inthe X-axis direction with respect to the base 102 when the first andsecond cradle arms 112 a/112 b pivot about the first and second hinges110 a/110 b. The cradle opening 116 can receive a striker pin 117 thatmay be formed against a second panel (not shown in FIG. 1) as discussedin greater detail below.

The base arms 108 a/108 b each include a respective base recess 118a/118 b formed therein, and the cradle arms each include a respectivecradle recess 120 a/120 b formed therein. The differential motion sensor100 further contains at least one conductive fuse. According to thenon-limiting embodiment illustrated in FIG. 1, a first conductive fuse122 a and a second conductive fuse 122 b are provided to improvereliability and monitoring redundancy (e.g. Channel A and Channel B) ofthe differential motion sensor 100. It is appreciated, however, that thedifferential motion sensor 100 can be formed with only a singleconductive fuse. Each conductive fuse 122 a/122 b includes a cradleportion 124 a/124 b and a base portion 126 a/126 b. The cradle portion124 a/124 b is disposed in a respective cradle recess 120 a/120 b and issupported therein via a cradle bolt 128 a/128 b. The base portion 126a/126 b is disposed in a respective base recess 118 a/118 b and issupported therein via a base bolt 130 a/130 b. The cradle portion 124a/124 b of the fuse and the base portion 126 a/126 b of the fuse areconductively connected to each other at a fracture region 132 a/132 b,which inhibits the discharge sensor from pivoting when a force (i.e., ashear force) applied to the fracture region 132 a/132 b is less than afracturing force threshold. According to a non-limiting embodiment, thefracture region 132 a/132 b is interposed between the base 102 and thecradle 104.

The differential motion sensor 100 according to the non-limitingembodiment of FIG. 2A is illustrated with a 2:1 cradle ratio. That is,the cradle arms 112 a/112 b have a length that is twice the length ofthe base arms 108 a 108 b. Accordingly, a pin force of approximately 95lbs, for example, would shear the fracture regions 132 a/132 b of thefirst and second conductive fuses 122 a/122 b, which each fracture atapproximately 95 lbs. It is appreciated, however, the cradle ratio ofthe differential motion sensor 100 can be varied to provide a lower pinforce/longer pin motion necessary to shear the fracture regions 132a/132 b, or a higher pin force/shorter pin motion necessary to shear thefracture regions 132 a/132 b. In other words, the cradle ratio can beadjusted according to a particular design application of thedifferential motion sensor. If less force (e.g., pin force) is desiredto pivot the cradle 104 and sever the conductive fuse 122 a/122 b, forexample, the length of the cradle arms 112 a/112 b can be increased fromtwice the length of the base arms 108 a/108 b to three-times the lengthof the base arms 108 a/108 b. The pin force (F_(p)) can be calculatedaccording to the equation:F _(p)=2F _(S)/(R _(C)) where,

F_(p)=the pin force;

F_(S)=the shear force required to fracture each fuse; and

R_(C)=the cradle ratio.

Although the pin force (F_(p)) described in the equation above reflectsan embodiment where two fuses 126 a/126 b are implemented such that twoshear forces (2F_(S)) are considered, it is appreciated that the pinforce (F_(p)) may be determined in a similar manner where only a singlefuse 126 is implemented and thus a single shear force (F_(S)) isconsidered. The shear force (F_(S)) necessary to fracture the fuseloaded in shear is typically approximately 58% of the tensile force(F_(T)) necessary to fracture the fuse loaded in tension. Accordingly,at least one embodiment of the disclosure utilizes shear loading tosever the fracture regions 132/132 b instead of tensile force (i.e.,pulling force in the Z-direction) to provide a differential motionsensor 100 with increased sensitivity with respect to conventionalsensors that operate according to tensile loading.

The first and second conductive fuses 122 a/122 b include one or moreconductive terminals 134 a/136 a and 134 b/136 b. One or more wires (notshown) can be electrically connected to the terminals 134 a/136 a and134 b/136 b. In this manner, electrical current provided from a powersource (not shown) can flow from the terminals 134 a/136 a and 134 b/136b, or vice versa, when the fracture region 132 a/132 b is conductivelyconnected.

The differential motion sensor 100 is configured to operate in a firstmode (e.g., a closed-circuit mode) and a second mode (e.g., anopen-circuit mode) based on the position of the cradle 104 with respectto the base 102. For example, the differential motion sensor 100 isconfigured to operate in a first mode when the cradle 104 is alignedwith the base 102, and a second mode when the cradle 104 is pivotablydisplaced (i.e., misaligned) with respect to the base 102. Displacingthe cradle 104 with respect to the base 102 causes the conductive fuse122 a/122 b to sever in the second mode.

According to a non-limiting embodiment, the differential motion sensor100 operates in the first mode when the fracture region 132 a/132 b isconductively connected (i.e., not severed) such that current flowsbetween the fuse terminals 134 a/136 a and 134 b/136 b. The differentialmotion sensor, however, operates in the second mode when the fractureregion 132 a/132 b is not conductively connected (i.e., severed) suchthat current prevented from flowing between the terminals 134 a/136 aand 134 b/136 b. When the second mode is effected, a control module (notshown) can detect the stoppage of said current flow. In this manner, thecontrol module can determine that a force applied to differential motionbetween the cradle 104 and the pin 117 has exceeded the thresholdthereby severing one or more of the fracture regions 132 a/132 b andplacing the differential motion sensor in the open-circuit mode.

Referring to FIG. 2A, the differential motion sensor 100 is illustratedin a closed-circuit mode according to a non-limiting embodiment. In thisscenario, the base 102 is coupled to a first panel 200. A second panel202 includes a striker pin 117. The striker pin 117 includes a first endconnected to the second panel 202 and an opposing second end thatextends into the cradle opening 116. The panels 200 and 202 normallymove in unison together along the X-axis direction such that the strikerpin 117 is stably maintained within the cradle opening 116. The strikerpin 117, therefore, does not apply a force against either the first orsecond crossbars 114 a/114 b such that the cradle 104 is not forced topivot. Accordingly, the force threshold is not exceeded and the fractureregion 132 a/132 b remains electrically connected thereby maintainingthe differential motion sensor in the closed-circuit mode.

Turning now to FIG. 2B, the differential motion sensor 100 isillustrated in an open-circuit mode according to a non-limitingembodiment. In this scenario, the second panel 202 is displaced adistance (d) with respect to the first panel 200 such that the motionsof the first and second panels 200/202 are not synchronized. As aresult, the striker pin 117 is displaced in the pivoting direction ofthe cradle 104 (i.e., the X-axis) and contacts the second crossbar 114b, for example, thereby inducing a moment about the hinges 110 a/110 bwhich is resisted by the conductive fuses. When the moment exceeds thethreshold, the fracture region 132 a/132 b of the first and/or secondconductive fuses 122 a/122 b is fractured in shear and the cradle 104 isallowed to pivot further about the hinges 110 a/110 b and in theX-direction. The severed fracture region 132 a/132 b, however,disconnects (i.e., stops) current flow between the terminals 134 a/136 aand/or terminals 134 b/136 b thereby initiating the open-circuit mode ofthe differential motion sensor 100. In response to detecting thestoppage of current (i.e., the open-circuit mode), the control moduledetermines that the first panel and/or the second panel are displaced.

According to at least one embodiment, the differential motion sensor 100provides sense detection along a single axis. That is, the motion of thecradle 104 needed to fracture one or more of the fracture regions 132a/132 b is in the X-axis direction, for example, and is independent ofthe Y-axis direction and the Z-axis direction. As a result, any relativespanwise motions between the surfaces being monitored, in either theY-axis and/or Z axis directions, has no influence on the forces reactedat the fuse(s) and thereby resulting in a more predictable sensorperformance. In addition, since the fracture regions 132 a/132 boriented to fail in shear, as opposed to a tension, the necessary forceapplied by the striker pin 117 to sever the fracture region 132 a/132 bis reduced. Accordingly, the possibility of the first and secondfracture regions 132 a/132 b remaining dormant (i.e., intact) followinga striking force applied by the striker pin 117 is reduced.

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Also, in the drawings andthe description, there have been disclosed exemplary embodiments of theinvention and, although specific terms may have been employed, they areunless otherwise stated used in a generic and descriptive sense only andnot for purposes of limitation, the scope of the invention therefore notbeing so limited. Moreover, the use of the terms first, second, etc., donot denote any order or importance, but rather the terms first, second,etc., are used to distinguish one element from another. Furthermore, theuse of the terms a, an, etc. do not denote a limitation of quantity, butrather denote the presence of at least one of the referenced item.

What is claimed is:
 1. A differential motion sensor configured to detecta shear force applied to an aircraft, comprising: a base including afirst surface extending along a first axis to define a length and asecond axis to define a width, and including at least one hinge thatpivots about a rotational axis extending along the first axis; a cradlepivotably coupled to the at least one hinge and configured to move in adirection of the second axis when pivoting about the hinge; and at leastone conductive fuse extending along a third axis that is perpendicularto both the first axis and the second axis, the at least one conductivefuse including first and second fuse portions connected to one anotherat a fracture region; wherein the fracture region extends along thesecond axis such that the first and second fuse portions are configuredto sever at the fracture region when a shear force applied to thedifferential motion sensor along the second axis exceeds a forcethreshold of the at least one conductive fuse, and wherein thedifferential motion sensor is configured to operate in a first mode whenthe cradle is aligned with the base and a second mode when the cradle ispivotably displaced with respect to the base, a first conductiveterminal connected to the first fuse portion and a second conductiveterminal connected to the second fuse portion, the first and secondconductive terminals configured to deliver electrical current throughthe at least one conductive fuse, wherein the differential motion sensoris configured to operate in a first mode in response to the currentflowing through the at least one conductive fuse and a second mode inresponse to fracturing the at least one conductive fuse at the fractureregion such that the current does not flow through the at least oneconductive fuse.
 2. The differential motion sensor of claim 1, whereinthe first fuse portion and the second fuse portion each extending alongthe third axis.
 3. The differential motion sensor of claim 1, whereinthe fracture region is interposed between the cradle and the base. 4.The differential motion sensor of claim 3, wherein the cradle includes asecond surface having an opening for receiving a striker pin.
 5. Thedifferential motion sensor of claim 4, wherein the base furthercomprises: a first base arm including a first hinge formed therein and asecond base arm including a second hinge formed therein in, the firstand second base arms formed at opposite ends of the base and extendingtherefrom along the third axis, and wherein the cradle furthercomprises: a first cradle arm including a first end coupled to thesecond surface and a second end pivotably coupled to the first hinge, asecond cradle arm including a first end coupled to the second surfaceand a second end pivotably coupled to the second hinge.
 6. Thedifferential motion sensor arm of claim 5, where the first and secondbase arms have a first length, and the first and second cradle arms havea second length that is greater than the first length.
 7. A method ofdetecting displacement of a first object installed on an aircraft withrespect to a second object installed on the aircraft, the methodcomprising, comprising: forming a base on the first object, the baseincluding a first surface extending along a first axis to define alength and a second axis to define a width, and pivotably connecting acradle to the base such that the cradle is configured to move in adirection of the second axis; flowing current through at least oneconductive fuse formed on the differential motion sensor, the at leastone conductive fuse including first and second fuse portions connectedto one another at a fracture region, the fracture region extending alongthe second axis; detecting that the first and second objects are alignedwith respect to one another when the cradle when the current flowsthrough the at least one conductive fuse, and detecting that the firstand second objects are displaced with respect to one another when thecradle is pivotably displaced with respect to the base such that thefirst and second fuse portions sever at the fracture region in responseto a shear force applied to the differential motion sensor along thesecond axis exceeding a force threshold of the at least one conductivefuse to disconnect current flow through the at least one conductivefuse.
 8. The method of claim 7, further comprising detecting that thefirst and second objects are displaced with respect to one another basedon the shear force.
 9. The method of claim 8, further comprisingpivoting the cradle about a rotational axis extending along the firstaxis to induce the shear force.
 10. The method of claim 9, furthercomprising forming a first end of a striker pin to the second object andextending a second end of the striker pin into an opening formed in thecradle such that the striker pin applies the shear force on the at leastone conductive fuse when the first and second objects are displaced withrespect to one another.